ANTIOXIDATIVE ACTIVITY OF AN ISOFLAVONOID, 2''-O-GLYCOSYLISOVITEXIN ISOLATED FROM GREEN BARLEY LEAVES

A flavonoid, 2"-O-glycosylisovitexin (2"-O-GIV), with antioxidative activity previously proved by the thiobarbituric acid method, was isolated from young green barley leaves. Antioxidative activity of 2"-O-GIV was determined by using gas chromatography to measure amounts of malonaldehyde (MA) formed from squalene and ethyl linoleate upon UV irradiation or with Fenton's reagent. 2"-O-GIV suppressed the formation of MA from squalene upon oxidation with Fenton's reagent 32% at the level of 150 muM/75 muL of squalene. 2"-O-GIV decreased MA formation from ethyl linoleate upon UV irradiation to 40% at pH 7.4; no significant effect was observed at pH 3.5 and 11. 2"-O-GIV (100 muM) decreased MA formation from ethyl linoleate (10 muL) with Fenton's reagent to 59% and 10% at pH 3.5 and 7.4, respectively. 2"-O-GIV showed antioxidative activities almost equal to that of alpha-tocopherol in all of the experiments.